In control circuits for semiconductor switches, in particular in control circuits for power semiconductor switches, a primary side and a secondary side can be galvanically isolated by means of an isolating transformer. That can protect the circuits at the primary side from the potentially high switched voltages on the secondary side. However, in such systems and in some situations, changes in potential at the semiconductor switch as a result of parasitic coupling capacitances, in particular coupling capacitances of the isolating transformer, can generate a current between the primary side and the secondary side via the isolating transformer. That can lead to the occurrence of interference signals which may be erroneously identified as control signals or may result in that the correct control signals are not identified. As a consequence, the semiconductor switch may be switched on or off in an undesired manner. A reduction of the coupling capacitance of the transformer has been proposed to alleviate this problem. That can be achieved in some examples by providing a capacitive shielding or the largest possible distance between a primary winding and a secondary winding of an isolating transformer.